The present invention generally relates to air cycle Environmental Control Systems (ECSs). More specifically, the invention relates to an improved air cycle ECS and improved method of conditioning water vapor compressed air by omitting the use of a condenser to condense water vapor while still increasing efficiency and lowering production costs.
ECSs are used to provide a supply of conditioned air to an enclosure, such as an aircraft cabin and cockpit. In the past, an air cycle ECS has typically operated on a flow of bleed air taken from an intermediate or high pressure stage within a jet engine having multi-compression stages. The bleed air has usually been pre-cooled within a primary heat exchanger with heat being dumped to RAM air and then flowed to a compressor. After compression, the air has been routed through a series of heat exchangers, including a reheater and a condenser. Then, the air has typically been expanded by a turbine which is mechanically engaged to the compressor. Finally, the air can be sent to the cabin.
Past air cycle ECS designs have included 3 wheel and 4 wheel bootstrap, high pressure water separation cycles. The 3 wheel and 4 wheel designs utilize a reheater and a condenser heat exchanger to respectively pre-cool the bleed air and then condense the moisture in the air. After condensation, the condensed water is removed by a water extractor. The resulting dehumidified air flows to the reheater to recover energy and then to a turbine for expansion and consequent cooling. The expanded air from the turbine can then be used to cool and condense water in the condenser heat exchanger. For the 3 wheel system, the expanded air which has been warmed in the condenser can then be directly supplied to a cabin. In the 4 wheel design, the expanded air which has been warmed in the condenser is then further expanded by another turbine for eventual supply to the cabin.
While the past 3 wheel and 4 wheel bootstrap systems have been useful, unsatisfied needs still remain. For example, size constraints continue to call for smaller systems. Obviously, the smaller the ECS, the more cooling capacity can be provided within a given system space. And with a smaller ECS, there are a greater number of opportunities that the ECS can be used as a retrofit. As another example, system reliability means lower maintenance costs. Greater reliability of the ECS can be achieved by requiring fewer components in the ECS, since there will be fewer components which can fail. Furthermore, with fewer system components, the overall cost of the system will decrease. Yet another example of an unmet need is system efficiency. If energy is being wasted by parasitic losses to system components, fewer components means less waste and greater efficiency.
As can be seen, there is a need for an improved air cycle ECS and improved method of conditioning high pressure water vapor bearing air which eliminates system components typically used in past systems. There is also a need for such improved systems and methods which reduce the overall system size and, in turn, improve reliability and efficiency, in addition to lowering the system cost.